1004 COMPREHENSIVE KEY 



(See note on Leptoihrix and Thiothrix {vide supra 7 and 10).) 



Trichomes 12 



12. Trichomes attached; free cells formed bj' abstriction from the terminal portion are 



motile by a gliding action on a solid surface Leucothrix p. 850 



Note: Although Harold and Stanier claim that Leucothrix does not form a 

 sheath, they consider it to be identical with Pontothrix, which was originally 

 recorded as a sheathed organism. 

 Not as above; if motile, whole trichomes move; cells within the trichomes each contain 

 one or more pseudovacuoles which give a reddish gleam in transmitted light 13 



13. Trichomes occur singly Pelonema p. 271 



Trichomes occur in bundles Peloploca p. 270 



Note: Peloploca is described as "sheath not demonstrated." It is included 

 here on the possibility that it is sheathed and because of the morphological 

 similarity to Pelonema. 



14. Trichomes 6 to 20 microns long; motile by means of peritrichous fiagella; rigid, multi- 



cellular, bacillary forms in which the stained cells are differentiated into a series of 

 light and dark bands; end cells rounded; commonly form chains up to 200 microns 

 long. Individual cells in a trichome may separate as discoid elements and may grow 

 out into filaments; common in peat and cow dung Caryophanon p. 831 



General morphology similar to that found in Caryophanon, but individual trichomes 

 are shorter and usually composed of 4 cells or 4 cell -pairs; trichomes are chain-form- 

 ing but non-motile; recorded from the oral cavity of man and domestic animals 



Simonsiella p. 833 



Not as above 15 



15. Long trichomes attached by a globular holdfast to the intestinal walls of some insects 



and millipeds; a single endospore may be produced in any or all cells of the trichome, 

 and if so, it usually lies in an oblique position Arthromitus p. 835 



Trichomes 1.5 to 22.0 microns long; found in the cytoplasm of the rhizopod Pelomyxa 

 palustris, generally aggregated close to the nucleus Cladothrix p. 930 



Not as above 16 



16. Entire trichomes unattached and actively motile by a gliding action on a solid surface; 



no flagella 17 



Trichomes attached or free; non -motile; abstricted cells may be motile with a gliding 



action on solid surfaces 19 



Note: References have been made in the literature to the multicellular nature 

 of many small cells previously regarded as unicellular. They are mostly cells 

 not more than 6 microns long and will be found by other characteristics to 

 belong to genera located in Section F et seq. 



17. Organisms oxidize hydrogen sulfide, depositing sulfur inside the cell 



Beggiatoa p. 838 

 Not as above 18 



18. Trichomes composed of cells which are not clearly articulated at the junctions; com- 



plete trichomes very flexible Vitreoscilla p. 845 



Trichomes composed of rod-like elements with little individual flexibility; bending 

 occurs freely at the junctions Bactoscilla p. 848 



19. Colorless trichomes; attached; cells are abstricted from the terminal position and 



are motile by a gliding action on a solid surface. Sulfur is not deposited internally 



Leucothrix p. 850 

 Colorless trichomes; arranged in bundles; non -motile; each cell in the trichome con- 

 tains one or more gas vacuoles which gleam reddish in transmitted light 



Peloploca p. 270 



Cells deposit sulfur internally Thiothrix p. 842 



Note: Thiothrix is inserted here although classical descriptions of the genus 

 indicate a sheath. 



